Gas turbine engine with geared architecture

ABSTRACT

A gas turbine engine includes a bypass ratio greater than about ten (10). A fan is supported on a fan shaft and has a plurality of fan blades. A gear system is connected to the fan shaft and a plurality of planetary gears. A first set of opposed angled ring gear teeth are separated from a second set of opposed angled ring gear teeth. A lubricant flow path is located axially between the first set of opposed angled ring gear teeth and the second set of opposed angled ring gear teeth. An annular channel axially is aligned with the lubricant flow path. A low pressure turbine has an inlet, an outlet, and a low pressure turbine pressure ratio greater than 5:1. A low fan pressure ratio is less than 1.45 across the fan blade alone.

CROSS REFERENCE TO RELATED APPLICATIONS

The present disclosure is a continuation of U.S. patent application Ser.No. 16/122,236 filed Sep. 5, 2018, which is a continuation of U.S.patent application Ser. No. 15/892,210, filed Feb. 8, 2018, now U.S.Pat. No. 10,082,105, granted Sep. 25, 2018, which is a continuation ofU.S. patent application Ser. No. 14/753,048, filed Jun. 29, 2015, nowU.S. Pat. No. 10,107,231, granted Oct. 23, 2018, which was acontinuation-in-part of U.S. patent application Ser. No. 13/346,120,filed Jan. 9, 2012, which was a continuation-in-part of U.S. patentapplication Ser. No. 11/504,220, filed Aug. 15, 2006, now U.S. Pat. No.8,753,243, granted Jun. 17, 2014.

BACKGROUND OF THE INVENTION

This invention relates to a ring gear used in an epicyclic gear train ofa gas turbine engine.

Gas turbine engines typically employ an epicyclic gear train connectedto the turbine section of the engine, which is used to drive the turbofan. In a typical epicyclic gear train, a sun gear receives rotationalinput from a turbine shaft through a compressor shaft. A carriersupports intermediate gears that surround and mesh with the sun gear. Aring gear surrounds and meshes with the intermediate gears. Inarrangements in which the carrier is fixed against rotation, theintermediate gears are referred to as “star” gears and the ring gear iscoupled to an output shaft that supports the turbo fan.

Typically, the ring gear is connected to the turbo fan shaft using aspline ring. The spline ring is secured to a flange of the turbo fanshaft using circumferentially arranged bolts. The spline ring includessplines opposite the flange that supports a splined outercircumferential surface of the ring gear. The ring gear typicallyincludes first and second portions that provide teeth facing in oppositedirections, which mesh with complimentary oppositely facing teeth of thestar gears.

An epicyclic gear train must share the load between the gears within thesystem. As a result, the splined connection between the ring gear andspline ring is subject to wear under high loads and deflection. Sincethe spline connection requires radial clearance, it is difficult to geta repeatable balance of the turbo fan assembly. Balance can alsodeteriorate over time with spline wear.

SUMMARY

In one exemplary embodiment, a gas turbine engine includes a bypassratio greater than about ten (10). A fan is supported on a fan shaft andhas a plurality of fan blades. There is a gutter with an annularchannel. A gear system is connected to the fan shaft. There is aplurality of planetary gears and a ring gear with an aperture that isaxially aligned with the annular channel. The ring gear includes a firstportion with a first set of opposed angled teeth separated by a troughfrom a second portion with a second set of opposed angled teeth. Atorque frame at least partially supports the gear system. A low pressureturbine has an inlet, an outlet, and a low pressure turbine pressureratio greater than 5:1 and a low fan pressure ratio of less than 1.45across the fan blade alone.

In a further embodiment of any of the above, a support relative to afixed housing facilitates segregation of vibrations.

In a further embodiment of any of the above, there is an input to thegear system that facilitates segregation of vibrations.

In a further embodiment of any of the above, the gear system includes asun gear that has a sun gear splined connection.

In a further embodiment of any of the above, the input includes an inputsplined connection complementary to the sun gear splined connection. Thegear system includes a gear reduction ratio of greater than 2.5.

In a further embodiment of any of the above, the fan shaft is supportedby at least one tapered roller bearing.

In a further embodiment of any of the above, a fan tip speed less than1150 ft/second.

In a further embodiment of any of the above, a fan tip speed is lessthan 1150 ft/second. A fan is on a fan shaft and has a plurality of fanblades and a low fan pressure ratio of less than 1.45 across the fanblades alone.

In a further embodiment of any of the above, the first portion and thesecond portion of the ring gear each include a radially extending flangethat extends radially outward away from a corresponding set of opposedangled teeth. The fan shaft includes a radially extending flangeconnected to the radially extending flange on the first portion of thering gear and the radially extending flange on the second portion of thering gear.

In a further embodiment of any of the above, a seal is attached to atleast one of the radially extending flanges on the ring gear or theradially extending flange on the fan shaft.

In a further embodiment of any of the above, the seal includes an oilreturn passage.

In a further embodiment of any of the above, the oil return passageincludes a slot.

In a further embodiment of any of the above, the slot is located in theseal.

In a further embodiment of any of the above, the slot is located in theradially extending flange on the fan shaft.

In a further embodiment of any of the above, the gutter is forcollecting oil expelled from the gear system.

In a further embodiment of any of the above, a fan tip speed less than1150 ft/second.

In a further embodiment of any of the above, the gutter is formed from asoft material.

In a further embodiment of any of the above, the soft material isaluminum. In another exemplary embodiment, a gas turbine engine includesa fan supported on a fan shaft by at least one roller bearing and has aplurality of fan blades. A bypass ratio is greater than about ten (10).There is a gutter with an annular channel. A planetary gear system isconnected to the fan shaft. The gear system has a gear reduction ratioof greater than 2.5 and a plurality of intermediate gears. A ring gearwith an aperture is axially aligned with the annular channel. The ringgear includes a first portion separated from a second portion. The firstportion and the second portion each include a radially extending flangethat extends radially outward away from a corresponding set of opposedangled teeth. A torque frame is at least partially supporting the gearsystem with respect to the housing which facilitates the segregation ofvibrations and other transients.

In a further embodiment of any of the above, there is an input to thegear system which facilitates segregation of vibrations.

In a further embodiment of any of the above, the gear system includes asun gear that has a sun gear splined connection. The input includes aninput splined connection complementary to the sun gear splinedconnection.

In a further embodiment of any of the above, the roller bearing is atapered roller bearing.

In a further embodiment of any of the above, the gutter is forcollecting oil expelled from the gear system.

In a further embodiment of any of the above, the gutter is formed from asoft material.

In a further embodiment of any of the above, the soft material isaluminum.

In a further embodiment of any of the above, a low pressure turbine hasan inlet, an outlet, and a low pressure turbine pressure ratio greaterthan 5:1. A low fan pressure ratio of less than 1.45 which is measuredacross the fan blades alone.

In a further embodiment of any of the above, the fan shaft includes aradially extending flange which is connected to the radially extendingflange on the first portion of the ring gear and the radially extendingflange on the second portion of the ring gear.

In a further embodiment of any of the above, a seal is attached to atleast one of the radially extending flanges on the ring gear or theradially extending flange on the fan shaft.

In a further embodiment of any of the above, the seal includes an oilreturn passage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view of a front portion of a gasturbine engine illustrating a turbo fan, epicyclic gear train and acompressor section.

FIG. 2 is an enlarged cross-sectional view of the epicyclic gear trainshown in FIG. 1.

FIG. 3 is an enlarged cross-sectional view of an example ring gearsimilar to the arrangement shown in FIG. 2.

FIG. 4 is a view of the ring gear shown in FIG. 3 viewed in a directionthat faces the teeth of the ring gear in FIG. 3.

FIG. 5 shows another embodiment.

FIG. 6 shows yet another embodiment.

DETAILED DESCRIPTION

A portion of a gas turbine engine 10 is shown schematically in FIG. 1.The turbine engine 10 includes a fixed housing 12 that is constructedfrom numerous pieces secured to one another. A compressor section 14having compressor hubs 16 with blades are driven by a turbine shaft 25about an axis A. A turbo fan 18 is supported on a turbo fan shaft 20that is driven by a compressor shaft 24, which supports the compressorhubs 16, through an epicyclic gear train 22. The engine 10 is ahigh-bypass geared architecture aircraft engine. In one disclosed,non-limiting embodiment, the engine 10 bypass ratio is greater thanabout six (6) to ten (10), the gear train 22 is an epicyclic gear trainsuch as a planetary gear system or other gear system with a gearreduction ratio of greater than about 2.3 and the low pressure turbine18 has a pressure ratio that is greater than about 5. The engine 10 inone non-limiting embodiment is a high-bypass geared architectureaircraft engine. In one disclosed embodiment, the engine 10 bypass ratiois greater than ten (10:1), the turbofan diameter is significantlylarger than that of the low pressure compressor 16, and the low pressureturbine 27 a (shown schematically) has a pressure ratio that is greaterthan 5:1. As understood, the low pressure turbine 27 a is downstream ofat least one upstream, or high pressure turbine. The gear train 22 maybe an epicycle gear train such as a planetary gear system or other gearsystem with a gear reduction ratio of greater than 2.5:1. It should beunderstood, however, that the above parameters are only exemplary of oneembodiment of a geared architecture engine and that the presentinvention is applicable to other gas turbine engines including directdrive turbofans.

A significant amount of thrust is provided by the bypass flow B due tothe high bypass ratio. The fan 18 of the engine 10 is designed for aparticular flight condition—typically cruise at about 0.8M and about35,000 feet. The flight condition of 0.8 M and 35,000 ft, with theengine at its best fuel consumption—also known as “bucket cruiseTSFC”—is the industry standard parameter of lbm of fuel being burneddivided by lbf of thrust the engine produces at that minimum point. “Lowfan pressure ratio” is the pressure ratio across the fan blade alone,without the FEGV system 36. The low fan pressure ratio as disclosedherein according to one non-limiting embodiment is less than 1.45. “Lowcorrected fan tip speed” is the actual fan tip speed in ft/sec dividedby an industry standard temperature correction of [(Tambient degR)/518.7){circumflex over ( )}0.5]. The “Low corrected fan tip speed” asdisclosed herein according to one non-limiting embodiment is less than1150 ft/second.

The gear train 22 generally includes a fan drive gear system (FDGS) 100driven by the compressor shaft 24 through an input coupling 102. Theinput coupling 102 both transfers torque from the compressor shaft 24 tothe gear train 22 and facilitates the segregation of vibrations andother transients therebetween.

The input coupling 102 may include an interface spline 102 joined, by agear spline 106, to the sun gear 30. The sun gear 30 is in meshedengagement with multiple star gears 32. Each star gear 32 is also inmeshed engagement with rotating ring gear 38 that is mechanicallyconnected to the fan shaft 20. Since the star gears 32 mesh with boththe rotating ring gear 38 as well as the rotating sun gear 30, the stargears 32 rotate about their own axes to drive the ring gear 38. Therotation of the ring gear 38 is conveyed to the fan 20 through the fanshaft 20 to thereby drive the fan 18 at a lower speed than the turbineshaft 25.

In the example arrangement shown, the epicyclic gear train 22 is a stargear train. Referring to FIG. 2, the epicyclic gear train 22 includesthe sun gear 30 that is connected to the compressor shaft 24, whichprovides rotational input, by the splined connection. A carrier 26 isfixed to the housing 12 by a torque frame 28 using fingers (not shown)known in the art. The carrier 26 supports star gears 32 using journalbearings 34 that are coupled to the sun gear 30 by meshed interfacesbetween the teeth of sun and star gears 30, 32. Multiple star gears 32are arranged circumferentially about the sun gear 30. Retainers 36retain the journal bearings 34 to the carrier 26. A ring gear 38surrounds the carrier 26 and is coupled to the star gears 32 by meshedinterfaces. The ring gear 38, which provides rotational output, issecured to the turbo fan shaft 20 by circumferentially arrangedfastening elements, which are described in more detail below.

The torque frame 28 supports the carrier 26 with respect to the housing12 such as a front center body which facilitates the segregation ofvibrations and other transients therebetween. It should be understoodthat various gas turbine engine case structures may alternatively oradditionally be provided.

The fixed housing 12 may further include a number 1 and 1.5 bearingsupport frame 108 which is commonly referred to as a “K-frame” whichsupports the number 1 and number 1.5 bearing systems 110A, 110B tosupport the fan shaft 20 (FIG. 1). The number 1 and number 1.5 bearingsystems 110A, 110B may include tapered roller bearings which provide aline contact.

Referring to FIGS. 3 and 4, the ring gear 38 is a two-piece constructionhaving first and second portions 40, 42. The first and second portions40, 42 abut one another at a radial interface 45. A trough 41 separatesoppositely angled teeth 43 (best shown in FIG. 4) on each of the firstand second portions 40, 42. The arrangement of teeth 43 forces the firstand second portions 40, 42 toward one another at the radial interface45. The back side of the first and second portions 40, 42 includes agenerally S-shaped outer circumferential surface 47 that, coupled with achange in thickness, provides structural rigidity and resistance tooverturning moments. The first and second portions 40, 42 have a firstthickness T1 that is less than a second thickness T2 arranged axiallyinwardly from the first thickness T1. The first and second portions 40,42 include facing recesses 44 that form an internal annular cavity 46.

The first and second portions 40, 42 include flanges 51 that extendradially outward away from the teeth 43. The turbo fan shaft 20 includesa radially outwardly extending flange 70 that is secured to the flanges51 by circumferentially arranged bolts 52 and nuts 54, which axiallyconstrain and affix the turbo fan shaft 20 and ring gear 38 relative toone another. Thus, the spline ring is eliminated, which also reducesheat generated from windage and churning that resulted from the sharpedges and surface area of the splines. The turbo fan shaft 20 and ringgear 38 can be rotationally balanced with one another since radialmovement resulting from the use of splines is eliminated. An oil baffle68 is also secured to the flanges 51, 70 and balanced with the assembly.

Seals 56 having knife edges 58 are secured to the flanges 51, 70. Thefirst and second portions 40, 42 have grooves 48 at the radial interface45 that form a hole 50, which expels oil through the ring gear 38 to agutter 60 that is secured to the carrier 26 with fasteners 61 (FIG. 2).The direct radial flow path provided by the grooves 48 reduces windageand churning by avoiding the axial flow path change that existed withsplines. That is, the oil had to flow radially and then axially to exitthrough the spline interface. The gutter 60 is constructed from a softmaterial such as aluminum so that the knife edges 58, which areconstructed from steel, can cut into the aluminum if they interfere.Referring to FIG. 3, the seals 56 also include oil return passages 62provided by first and second slots 64 in the seals 56, which permit oilon either side of the ring gear 38 to drain into the gutter 60. In theexample shown in FIG. 2, the first and second slots 64, 66 are insteadprovided in the flange 70 and oil baffle 68, respectively.

FIG. 5 shows an embodiment 200, wherein there is a fan drive turbine 208driving a shaft 206 to in turn drive a fan rotor 202. A gear reduction204 may be positioned between the fan drive turbine 208 and the fanrotor 202. This gear reduction 204 may be structured and operate likethe gear reduction disclosed above. A compressor rotor 210 is driven byan intermediate pressure turbine 212, and a second stage compressorrotor 214 is driven by a turbine rotor 216. A combustion section 218 ispositioned intermediate the compressor rotor 214 and the turbine section216.

FIG. 6 shows yet another embodiment 300 wherein a fan rotor 302 and afirst stage compressor 304 rotate at a common speed. The gear reduction306 (which may be structured as disclosed above) is intermediate thecompressor rotor 304 and a shaft 308 which is driven by a low pressureturbine section.

Although a preferred embodiment of this invention has been disclosed, aworker of ordinary skill in this art would recognize that certainmodifications would come within the scope of this invention. For thatreason, the following claims should be studied to determine the truescope and content of this invention.

What is claimed is:
 1. A gas turbine engine comprising: a bypass ratiogreater than about ten (10); a fan supported on a fan shaft and having aplurality of fan blades; a gear system connected to the fan shaft, aplurality of planetary gears, a first set of opposed angled ring gearteeth separated from a second set of opposed angled ring gear teeth,wherein a lubricant flow path is located axially between the first setof opposed angled ring gear teeth and the second set of opposed angledring gear teeth; an annular channel axially aligned with the lubricantflow path; a low pressure turbine with an inlet, an outlet, and a lowpressure turbine pressure ratio greater than 5:1; and a low fan pressureratio of less than 1.45 across the fan blade alone.
 2. The gas turbineengine of claim 1, further comprising a low fan pressure ratio of lessthan 1.45 across the fan blades alone.
 3. The gas turbine engine ofclaim 2, further comprising a gear system support relative to a fixedhousing facilitating segregation of vibrations.
 4. The gas turbineengine of claim 3, further comprising a torque frame at least partiallysupporting the gear system, wherein the torque frame facilitatessegregation of vibrations.
 5. The gas turbine engine of claim 4, furthercomprising an input to the gear system, wherein the input facilitatessegregation of vibrations.
 6. The gas turbine engine of claim 5, whereinthe gear system includes a sun gear having a sun gear splinedconnection.
 7. The gas turbine engine of claim 6, wherein the inputincludes an input splined connection complementary to the sun gearsplined connection and said gear system includes a gear reduction ratioof greater than 2.5.
 8. The gas turbine engine of claim 7, wherein theannular channel is at least partially defined by a gutter.
 9. The gasturbine engine of claim 8, wherein the fan shaft is supported by atleast one tapered roller bearing.
 10. The gas turbine engine of claim 8,further comprising a fan tip speed less than 1150 ft/second.
 11. The gasturbine engine of claim 8, wherein said gutter is for collecting oilexpelled from the gear system.
 12. The gas turbine engine of claim 11,further comprising a fan tip speed less than 1150 ft/second.
 13. The gasturbine engine of claim 12, wherein the gutter is formed from a softmaterial.
 14. The gas turbine engine of claim 13, wherein the softmaterial is aluminum.
 15. The gas turbine engine of claim 8, wherein thefirst set of opposed angled ring gear teeth and the second set ofopposed angled ring gear teeth each include a radially extending flangethat extends radially outward away from a corresponding set of opposedangled ring gear teeth, and the fan shaft includes a radially extendingflange connected to the radially extending flange on the first set ofopposed angled ring gear teeth and the radially extending flange on thesecond set of opposed angled ring gear teeth.
 16. The gas turbine engineof claim 15, further comprising a seal attached to at least one of theradially extending flanges on the first and second set of opposed angledring gear teeth or the radially extending flange on the fan shaft. 17.The gas turbine engine of claim 16, wherein the seal includes an oilreturn passage.
 18. The gas turbine engine of claim 17, wherein the oilreturn passage includes a slot.
 19. The gas turbine engine of claim 18,wherein the slot is located in the seal.
 20. The gas turbine engine ofclaim 18, wherein the slot is located in the radially extending flangeon the fan shaft.
 21. A gas turbine engine comprising: a fan supportedon a fan shaft by at least one roller bearing and having a plurality offan blades; a bypass ratio greater than about ten (10); an epicyclicgear system connected to the fan shaft, the epicyclic gear system havinga gear reduction ratio of greater than 2.5, a plurality of intermediategears, and a ring gear with an aperture that is, wherein the ring gearincludes a first portion separated from a second portion, the firstportion and the second portion each include a radially extending flangethat extends radially outward away from a corresponding set of opposedangled teeth; and an annular channel axially aligned with the apertureand located radially outward from the aperture.
 22. The gas turbineengine of claim 21, further comprising an input to the gear system and atorque frame as least partially supporting the gear system with respectto a housing, wherein the input and the torque frame each facilitatessegregation of vibrations.
 23. The gas turbine engine of claim 21,wherein the gear system includes a sun gear having a sun gear connectionand the input includes an input connection complementary to the sun gearconnection.
 24. The gas turbine engine of claim 22, wherein the annularchannel includes a gutter for collecting oil expelled from the gearsystem.
 25. The gas turbine engine of claim 24, wherein the gutter isformed from aluminum.
 26. The gas turbine of claim 25, furthercomprising a low pressure turbine with an inlet, an outlet, and a lowpressure turbine pressure ratio greater than 5:1, and a low fan pressureratio of less than 1.45 and the low fan pressure ratio is measuredacross the fan blades alone.
 27. The gas turbine of claim 25, furthercomprising a low pressure turbine with an inlet, an outlet, and a lowpressure turbine pressure ratio greater than 5:1, a low fan pressureratio of less than 1.45 and the low fan pressure ratio is measuredacross the fan blades alone, and a gear system support relative to afixed housing facilitating segregation of vibrations.
 28. The gasturbine engine of claim 27, wherein the fan shaft includes a radiallyextending flange connected to the radially extending flange on the firstportion of the ring gear and the radially extending flange on the secondportion of the ring gear.
 29. The gas turbine engine of claim 28,further comprising a seal attached to at least one of the radiallyextending flanges on the ring gear or the radially extending flange onthe fan shaft, wherein the seal includes an oil return passage.
 30. Thegas turbine engine of claim 29, further comprising a fan tip speed lessthan 1150 ft/second.